Owls don"t need eyes in the ago of their heads to see what"s behind them — they deserve to just swivel their heads all the way around. In fact, countless owl species, such together the prohibition owl, have the right to rotate your heads 270 degrees in each direction, which method they can look come the left by rotating every the way to the right, or evil versa.

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But exactly how do they perform it there is no severing their arteries or avoiding blood from getting to the brain? an illustrator and also a doctor at the Johns Hopkins University school of medication teamed increase to discover out.

"Until now, brain imaging specialists choose me who attend to human injuries resulted in by trauma come arteries in the head and also neck have always been puzzled as to why rapid, twisting head motions did no leave countless owls lie dead on the woodland floor native stroke," said study author Dr. Philippe Gailloud, in a statement native the university.

If humans tried to turn our top so rapidly or far, we"d tear the lining of ours arteries, which would cause clots to kind and result in a punch (besides additionally breaking ours necks), he added. "The carotid and also vertebral arteries in the neck that most pets — including owls and humans — are really fragile and also highly susceptible to also minor tears the the courage lining."


Looking within owls


To acquire a glimpse the the owl"s blood vessels once their necks were turning, the duo injected dye right into the blood ship of a dozen dead owls and also used a CT scan to visualize the shimmering fluid spreading transparent the birds" arteries favor blood, stated Fabian de Kok-Mercado, that performed the work while gaining a master"s in clinical illustration in ~ Johns Hopkins. (He is currently an illustrator in ~ the Howard Hughes medical Institute in Chevy Chase, Md.) The researcher then twisted the dead owls" top to watch what happened.

After producing the CT scan images, the researcher injected a plastic-like substance right into the veins the dead snowy, prohibition and an excellent horned owls and dissected the animals, illustration the routes and locations of the vessels.


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Fabian de Kok-Mercado (left) and also Dr. Philippe Gailloud provide a CT scan to a dead owl to learn how its blood vessels resist the rapid, up-to-270-degree transforms their heads make. (Image credit: Fabian de Kok-Mercado and Dr. Philippe Gailloud)

They uncovered a variety of previously undiscovered and also unique traits, de Kok-Mercado told OurAmazingPlanet. For one, the owls" neck bones, or vertebrae, contain holes that room much bigger than those uncovered in various other birds or humans. In humans, the hole in the vertebra is about the same size together the artery, but in owls the hole is around 10 times larger than the artery, according to the study, published today (Jan. 31) in the newspaper Science. This holes, or canals, likely host air sacks expected to cushion the twisting movement of the head, de Kok-Mercado said.


"We also noticed ideal away that these canals were absent in the bottom 2 vertebra the the neck," de Kok-Mercado said. This provides the cord-like vessels some slack as soon as the bird twisted its head.

The huge holes and "slack" at the bottom of the neck aid explain why the vessels don"t break. But they don"t describe why the supply of blood isn"t cut off when an owl turns its head — with so much twisting, the vessels room bound to end up being partially blocked.

Blood come the brain

The team noticed that the vertebral artery enlarges slightly as it viewpoints the brain, i m sorry is unusual and also not viewed in numerous other pets (like the trunk of a tree, vessels generally acquire smaller as they gain farther from the heart). The writer think the these enlarged areas may function as reservoirs in i beg your pardon blood deserve to pool, so that the mind has extra blood to job-related with as the head swivels around, de Kok-Mercado said.

The blood vessels near the brain are likewise highly connected. A vessel called the patent trigeminal artery associate the front and also the ago of the owl"s brain, which helps supply the organ with as much blood together possible.

Why do owls should crane your necks come such severe degree? It"s due to the fact that their eyes are tubular, built practically like telescopes, providing them exceptional vision, de Kok-Mercado said. Yet unlike humans, who have around spherical eyes, owls cannot relocate them around easily, so they need to rotate your heads.

The detect is just another example of how the birds are perfectly adjusted to suit their environment, allowing them to see regardless of having fairly fixed eyes.

"I expect it offers people an ext of an appreciation of the life on this planet," de Kok-Mercado said.

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